# Stage 1 - measurement - mass

## Strategy

Students can:

• identify materials that are light or heavy
• use a pan balance to compare the masses of two objects
• use a pan balance to compare the masses of two objects

## Activities to support the strategy

### Activity 1: equal masses

Using a pan scale provide opportunities for students to obtain a level balance using different types of materials, e.g.

• continuous material (sand, rice, water)
• large objects (boxes, books, rocks)
• small objects (pebbles, marbles)

Choose an object. Ask students to collect things from around the room that might combine to have the same mass as the object, e.g. “The whiteboard rubber has the same mass as 6 textas and 3 paddle pop sticks.”

Repeat this activity many times, measuring the mass of different objects in the room and from the playground.

Discuss with the students why they selected particular informal units.

After students have had many opportunities to investigate mass using combined informal units, encourage them to use one type of informal unit to balance the same objects. Have them draw their results. Discuss the difference between using a number of different units compared to using the same unit to balance the objects.

### Activity 2 : balance investigation

Divide students in to small groups of 4-5. Have each group experiment with a pan balance (equal arm balance/balance scales) and a variety of materials, such as, beads, marbles, paddle pop sticks. If materials are limited have the students rotate around the materials. Students work with a minimum of direction and record their findings. Have a sharing time to discuss the results and note any findings about balance – A pan balance is balanced when the pans are exactly equal.

Have students perform a variety of prescribed activities using the pan scales.

Estimate how many pencils are needed to balance

• 5 marbles
• 10 bottle tops
• 3 shells

Students check their estimates using a pan scale and record their results. ‘I think 5 pencils will balance 5 marbles, but really I needed 8 pencils.’

Have students balance 3 marbles with

• plastic counters
• paper clips
• Ask: Do the counters balance the paper clips?

Students show how many paddle pop sticks are needed to balance 20 counters and record their findings,

• Example - 4 paddle pop sticks balance/ exactly equal 20 counters.
• From many objects provided, have students find two that balance.

### Activity 3: guess and check

Have students bring in a toy from home. In small groups students estimate how many unicubes would be needed to balance their toys.

Use a pan balance to check their estimations.

Record

Object Estimate Actual